The present invention relates to testing image transfer mechanisms of imaging systems. More specifically, the present invention relates to the use of thermographic sheet material to test heat-generating image transfer mechanisms in imaging systems such as printers.
Imaging systems such as printers, fax machines, and copiers are virtually omnipresent, and can be found in homes and offices worldwide. The development of such systems has facilitated improvements in communication that have in turn fostered an enormous change in the way people live and work. Telecommuting, paperless offices, and intra-office networks represent but a few examples of the advancements that have been made possible by modern imaging systems.
In imaging systems employing laser or electrophotographic printing, a latent image developed on a charged photoconductive drum or belt is exposed to toner to form a toner image. Then the toner image is transferred from the drum or belt to a print medium, typically sheet material such as paper. After, or concurrent with, the toner image transfer, the process involves the application of heat and pressure to the toner on the print medium, usually by a heated pressure roller backed by an idler roller. This process of heating the toner to secure it to the print medium is called fusing. Thus, the toner is said to be normally fused onto or into the print medium, using one or more heated fuser pressure rollers.
Consistent, high-quality printing requires the fusing system to heat the toner to a toner fusion temperature (e.g., approximately 190xc2x0 C.), and to do so evenly across the width and length of the print medium. Uneven heating can be caused by factors such as mechanical or electrical failure or toner buildup, and increases the likelihood of degraded print quality.
It can thus be seen that the need exists for a test mechanism to determine evenness of heat transfer in a fusing arrangement of an imaging system.
The present invention is directed in one embodiment to a heat transfer test assembly in an imaging system of a type wherein sheet material is passed through the imaging system and an image is formed on the sheet material, and the imaging system includes a heat transfer stage wherein heat is transferred to sheet material. The test assembly includes at least one test sheet having thermographic properties. The test assembly also includes a comparison sheet having indicia representing a thermographic sheet that has been passed through an satisfactorily functioning heat transfer stage of an imaging system. Comparison of a test sheet that has been passed through the imaging system with the comparison sheet provides information about the functioning of the imaging system.
The indicia on the comparison sheet can be provided as a graphical representation of a thermographic sheet that has been passed through an satisfactorily functioning heat transfer stage, such as a fusing system of a laser imaging system. The thermographic properties of the test sheet can extend across a substantial portion of the width and length of the test sheet. In an embodiment, the thermographic properties of the test sheet extend across the entire width and length of the test sheet.
The thermographic properties of the test sheet can be activated at a temperature of approximately 190xc2x0 C., and may provide a non-reversible and/or multicolored image.
A second embodiment of the invention is directed to a method of testing heat transfer within an imaging system. The imaging system is of a type wherein sheet material is passed through the imaging system and an image is formed on the sheet material, with the imaging system including a heat transfer stage wherein heat is transferred to sheet material. In a first step, at least one test sheet having thermographic properties is provided. The test sheet has dimensions enabling it to be passed through the imaging system. A comparison sheet including indicia representing a thermographic sheet that has been passed through an satisfactorily functioning heat transfer stage of an imaging system is provided. The at least one test sheet is passed through the imaging system, and then compared to the comparison sheet to gather information about the functioning of the imaging system.